Lighthouse performance scoring | Chrome for Developers

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how Lighthouse generates the overall Performance score for your page."> <meta property="og:description" content="Learn how Lighthouse generates the overall Performance score for your page."><meta property="og:url" content="https://developer.chrome.com/docs/lighthouse/performance/performance-scoring"><meta property="og:locale" content="en"><script type="application/ld+json"> { "@context": "https://schema.org", "@type": "Article", "dateModified": "2019-09-19", "headline": "Lighthouse performance scoring" } </script><script type="application/ld+json"> { "@context": "https://schema.org", "@type": "BreadcrumbList", "itemListElement": [{ "@type": "ListItem", "position": 1, "name": "Docs", "item": "https://developer.chrome.com/docs" },{ "@type": "ListItem", "position": 2, "name": "Lighthouse", "item": "https://developer.chrome.com/docs/lighthouse" },{ "@type": "ListItem", "position": 3, "name": "Lighthouse performance scoring", "item": 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<devsite-appearance-selector></devsite-appearance-selector> <devsite-language-selector> <ul role="presentation"> <li role="presentation"> <a role="menuitem" lang="en" >English</a> </li> <li role="presentation"> <a role="menuitem" lang="de" >Deutsch</a> </li> <li role="presentation"> <a role="menuitem" lang="es_419" >Español – América Latina</a> </li> <li role="presentation"> <a role="menuitem" lang="fr" >Français</a> </li> <li role="presentation"> <a role="menuitem" lang="id" >Indonesia</a> </li> <li role="presentation"> <a role="menuitem" lang="it" >Italiano</a> </li> <li role="presentation"> <a role="menuitem" lang="nl" >Nederlands</a> </li> <li role="presentation"> <a role="menuitem" lang="pl" >Polski</a> </li> <li role="presentation"> <a role="menuitem" lang="pt_br" >Português – Brasil</a> </li> <li role="presentation"> <a role="menuitem" lang="vi" >Tiếng Việt</a> </li> <li role="presentation"> <a role="menuitem" lang="tr" >Türkçe</a> </li> <li role="presentation"> <a role="menuitem" lang="ru" >Русский</a> </li> <li role="presentation"> <a role="menuitem" lang="he" >עברית</a> </li> <li role="presentation"> <a role="menuitem" lang="ar" >العربيّة</a> </li> <li role="presentation"> <a role="menuitem" lang="fa" >فارسی</a> </li> <li role="presentation"> <a role="menuitem" lang="hi" >हिंदी</a> </li> <li role="presentation"> <a role="menuitem" lang="bn" >বাংলা</a> </li> <li role="presentation"> <a role="menuitem" lang="th" >ภาษาไทย</a> </li> <li role="presentation"> <a role="menuitem" lang="zh_cn" >中文 – 简体</a> </li> <li role="presentation"> <a role="menuitem" lang="zh_tw" >中文 – 繁體</a> </li> <li role="presentation"> <a role="menuitem" lang="ja" >日本語</a> </li> <li role="presentation"> <a role="menuitem" lang="ko" >한국어</a> </li> </ul> </devsite-language-selector> <devsite-user enable-profiles id="devsite-user"> <span class="button devsite-top-button" aria-hidden="true" visually-hidden>Sign in</span> </devsite-user> </div> </div> </div> <div class="devsite-collapsible-section "> <div class="devsite-header-background"> <div class="devsite-product-id-row" > <div class="devsite-product-description-row"> <ul class="devsite-breadcrumb-list" > <li class="devsite-breadcrumb-item "> <a href="https://developer.chrome.com/docs/lighthouse" class="devsite-breadcrumb-link gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Lower Header" data-value="1" track-type="globalNav" track-name="breadcrumb" track-metadata-position="1" track-metadata-eventdetail="Lighthouse" > Lighthouse </a> </li> </ul> </div> </div> <div class="devsite-doc-set-nav-row"> <devsite-tabs class="lower-tabs"> <nav class="devsite-tabs-wrapper" aria-label="Lower tabs"> <tab > <a href="https://developer.chrome.com/docs/lighthouse" track-metadata-eventdetail="https://developer.chrome.com/docs/lighthouse" class="devsite-tabs-content gc-analytics-event " track-type="nav" track-metadata-position="nav - lighthouse" track-metadata-module="primary nav" data-category="Site-Wide Custom Events" data-label="Tab: Lighthouse" track-name="lighthouse" > Lighthouse </a> </tab> <tab > <a href="https://developer.chrome.com/docs/lighthouse/overview" track-metadata-eventdetail="https://developer.chrome.com/docs/lighthouse/overview" class="devsite-tabs-content gc-analytics-event " track-type="nav" track-metadata-position="nav - get started" track-metadata-module="primary nav" data-category="Site-Wide Custom Events" data-label="Tab: Get started" track-name="get started" > Get started </a> </tab> <tab class="devsite-active"> <a href="https://developer.chrome.com/docs/lighthouse/performance/performance-scoring" track-metadata-eventdetail="https://developer.chrome.com/docs/lighthouse/performance/performance-scoring" class="devsite-tabs-content gc-analytics-event " track-type="nav" track-metadata-position="nav - performance audit" track-metadata-module="primary nav" aria-label="Performance audit, selected" data-category="Site-Wide Custom Events" data-label="Tab: Performance audit" track-name="performance audit" > Performance audit </a> </tab> <tab > <a href="https://developer.chrome.com/docs/lighthouse/accessibility/scoring" track-metadata-eventdetail="https://developer.chrome.com/docs/lighthouse/accessibility/scoring" class="devsite-tabs-content gc-analytics-event " track-type="nav" track-metadata-position="nav - accessibility audit" track-metadata-module="primary nav" data-category="Site-Wide Custom Events" data-label="Tab: Accessibility audit" track-name="accessibility audit" > Accessibility audit </a> </tab> <tab > <a href="https://developer.chrome.com/docs/lighthouse/best-practices/doctype" track-metadata-eventdetail="https://developer.chrome.com/docs/lighthouse/best-practices/doctype" class="devsite-tabs-content gc-analytics-event " track-type="nav" track-metadata-position="nav - best practices audit" track-metadata-module="primary nav" data-category="Site-Wide Custom Events" data-label="Tab: Best Practices audit" track-name="best practices audit" > Best Practices audit </a> </tab> <tab > <a href="https://developer.chrome.com/docs/lighthouse/seo/meta-description" track-metadata-eventdetail="https://developer.chrome.com/docs/lighthouse/seo/meta-description" class="devsite-tabs-content gc-analytics-event " track-type="nav" track-metadata-position="nav - seo audit" track-metadata-module="primary nav" data-category="Site-Wide Custom Events" data-label="Tab: SEO audit" track-name="seo audit" > SEO audit </a> </tab> </nav> </devsite-tabs> </div> </div> </div> </div> </devsite-header> <devsite-book-nav scrollbars > <div class="devsite-book-nav-filter" > <span class="filter-list-icon material-icons" aria-hidden="true"></span> <input type="text" placeholder="Filter" aria-label="Type to filter" role="searchbox"> <span class="filter-clear-button hidden" data-title="Clear filter" aria-label="Clear filter" role="button" tabindex="0"></span> </div> <nav class="devsite-book-nav devsite-nav nocontent" aria-label="Side menu"> <div class="devsite-mobile-header"> <button type="button" id="devsite-close-nav" class="devsite-header-icon-button button-flat material-icons gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Close navigation" aria-label="Close navigation"> </button> <div class="devsite-product-name-wrapper"> <a href="/" class="devsite-site-logo-link gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Site logo" track-type="globalNav" track-name="chromeForDevelopers" track-metadata-position="nav" track-metadata-eventDetail="nav"> <picture> <source srcset="https://www.gstatic.com/devrel-devsite/prod/v870e399c64f7c43c99a3043db4b3a74327bb93d0914e84a0c3dba90bbfd67625/chrome/images/lockup-dark-theme.svg" media="(prefers-color-scheme: dark)" class="devsite-dark-theme" alt="Chrome for Developers"> <img src="https://www.gstatic.com/devrel-devsite/prod/v870e399c64f7c43c99a3043db4b3a74327bb93d0914e84a0c3dba90bbfd67625/chrome/images/lockup.svg" class="devsite-site-logo" alt="Chrome for Developers"> </picture> </a> <span class="devsite-product-name"> <ul class="devsite-breadcrumb-list" > <li class="devsite-breadcrumb-item "> </li> </ul> </span> </div> </div> <div class="devsite-book-nav-wrapper"> <div class="devsite-mobile-nav-top"> <ul class="devsite-nav-list"> <li class="devsite-nav-item"> <a href="/case-studies" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Tab: Get inspired" track-name="get inspired" data-category="Site-Wide Custom Events" data-label="Responsive Tab: Get inspired" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Get inspired </span> </a> </li> <li class="devsite-nav-item"> <a href="/blog" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Tab: Blog" track-name="blog" data-category="Site-Wide Custom Events" data-label="Responsive Tab: Blog" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Blog </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs" class="devsite-nav-title gc-analytics-event devsite-nav-active" data-category="Site-Wide Custom Events" data-label="Tab: Docs" track-name="docs" data-category="Site-Wide Custom Events" data-label="Responsive Tab: Docs" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Docs </span> </a> <ul class="devsite-nav-responsive-tabs devsite-nav-has-menu "> <li class="devsite-nav-item"> <span class="devsite-nav-title" tooltip data-category="Site-Wide Custom Events" data-label="Tab: Docs" track-name="docs" > <span class="devsite-nav-text" tooltip menu="Docs"> More </span> <span class="devsite-nav-icon material-icons" data-icon="forward" menu="Docs"> </span> </span> </li> </ul> <ul class="devsite-nav-responsive-tabs"> <li class="devsite-nav-item"> <a href="/docs/lighthouse" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Tab: Lighthouse" track-name="lighthouse" data-category="Site-Wide Custom Events" data-label="Responsive Tab: Lighthouse" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Lighthouse </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/lighthouse/overview" class="devsite-nav-title gc-analytics-event devsite-nav-has-children " data-category="Site-Wide Custom Events" data-label="Tab: Get started" track-name="get started" data-category="Site-Wide Custom Events" data-label="Responsive Tab: Get started" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Get started </span> <span class="devsite-nav-icon material-icons" data-icon="forward" > </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/lighthouse/performance/performance-scoring" class="devsite-nav-title gc-analytics-event devsite-nav-has-children devsite-nav-active" data-category="Site-Wide Custom Events" data-label="Tab: Performance audit" track-name="performance audit" data-category="Site-Wide Custom Events" data-label="Responsive Tab: Performance audit" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip menu="_book"> Performance audit </span> <span class="devsite-nav-icon material-icons" data-icon="forward" menu="_book"> </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/lighthouse/accessibility/scoring" class="devsite-nav-title gc-analytics-event devsite-nav-has-children " data-category="Site-Wide Custom Events" data-label="Tab: Accessibility audit" track-name="accessibility audit" data-category="Site-Wide Custom Events" data-label="Responsive Tab: Accessibility audit" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Accessibility audit </span> <span class="devsite-nav-icon material-icons" data-icon="forward" > </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/lighthouse/best-practices/doctype" class="devsite-nav-title gc-analytics-event devsite-nav-has-children " data-category="Site-Wide Custom Events" data-label="Tab: Best Practices audit" track-name="best practices audit" data-category="Site-Wide Custom Events" data-label="Responsive Tab: Best Practices audit" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Best Practices audit </span> <span class="devsite-nav-icon material-icons" data-icon="forward" > </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/lighthouse/seo/meta-description" class="devsite-nav-title gc-analytics-event devsite-nav-has-children " data-category="Site-Wide Custom Events" data-label="Tab: SEO audit" track-name="seo audit" data-category="Site-Wide Custom Events" data-label="Responsive Tab: SEO audit" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > SEO audit </span> <span class="devsite-nav-icon material-icons" data-icon="forward" > </span> </a> </li> </ul> </li> <li class="devsite-nav-item"> <a href="/new" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Tab: New in Chrome" track-name="new in chrome" data-category="Site-Wide Custom Events" data-label="Responsive Tab: New in Chrome" track-type="globalNav" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > New in Chrome </span> </a> </li> </ul> </div> <div class="devsite-mobile-nav-bottom"> <ul class="devsite-nav-list" menu="_book"> <li class="devsite-nav-item devsite-nav-heading"><div class="devsite-nav-title devsite-nav-title-no-path"> <span class="devsite-nav-text" tooltip>Performance audit</span> </div></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/performance-scoring" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/performance-scoring" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/performance-scoring" ><span class="devsite-nav-text" tooltip>Scoring</span></a></li> <li class="devsite-nav-item devsite-nav-heading"><div class="devsite-nav-title devsite-nav-title-no-path"> <span class="devsite-nav-text" tooltip>Metrics</span> </div></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/first-contentful-paint" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/first-contentful-paint" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/first-contentful-paint" ><span class="devsite-nav-text" tooltip>First Contentful Paint</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/speed-index" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/speed-index" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/speed-index" ><span class="devsite-nav-text" tooltip>Speed Index</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/lighthouse-total-blocking-time" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/lighthouse-total-blocking-time" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/lighthouse-total-blocking-time" ><span class="devsite-nav-text" tooltip>Total Blocking Time</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/lighthouse-largest-contentful-paint" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/lighthouse-largest-contentful-paint" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/lighthouse-largest-contentful-paint" ><span class="devsite-nav-text" tooltip>Largest Contentful Paint</span></a></li> <li class="devsite-nav-item devsite-nav-external"><a href="https://web.dev/cls/" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: https://web.dev/cls/" track-type="bookNav" track-name="click" track-metadata-eventdetail="https://web.dev/cls/" ><span class="devsite-nav-text" tooltip>Cumulative Layout Shift</span><span class="devsite-nav-icon material-icons" data-icon="external" data-title="External" aria-hidden="true"></span></a></li> <li class="devsite-nav-item devsite-nav-heading"><div class="devsite-nav-title devsite-nav-title-no-path"> <span class="devsite-nav-text" tooltip>Opportunities</span> </div></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/render-blocking-resources" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/render-blocking-resources" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/render-blocking-resources" ><span class="devsite-nav-text" tooltip>Eliminate render-blocking resources</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/uses-responsive-images" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/uses-responsive-images" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/uses-responsive-images" ><span class="devsite-nav-text" tooltip>Properly size images</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/offscreen-images" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/offscreen-images" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/offscreen-images" ><span class="devsite-nav-text" tooltip>Defer offscreen images</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/unminified-css" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/unminified-css" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/unminified-css" ><span class="devsite-nav-text" tooltip>Minify CSS</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/unminified-javascript" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/unminified-javascript" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/unminified-javascript" ><span class="devsite-nav-text" tooltip>Minify JavaScript</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/unused-css-rules" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/unused-css-rules" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/unused-css-rules" ><span class="devsite-nav-text" tooltip>Remove unused CSS</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/uses-optimized-images" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/uses-optimized-images" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/uses-optimized-images" ><span class="devsite-nav-text" tooltip>Efficiently encode images</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/uses-webp-images" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/uses-webp-images" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/uses-webp-images" ><span class="devsite-nav-text" tooltip>Serve images in modern formats</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/uses-text-compression" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/uses-text-compression" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/uses-text-compression" ><span class="devsite-nav-text" tooltip>Enable text compression</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/uses-rel-preconnect" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/uses-rel-preconnect" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/uses-rel-preconnect" ><span class="devsite-nav-text" tooltip>Preconnect to required origins</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/server-response-time" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/server-response-time" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/server-response-time" ><span class="devsite-nav-text" tooltip>Reduce server response times</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/redirects" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/redirects" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/redirects" ><span class="devsite-nav-text" tooltip>Avoid multiple page redirects</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/uses-rel-preload" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/uses-rel-preload" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/uses-rel-preload" ><span class="devsite-nav-text" tooltip>Preload key requests</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/efficient-animated-content" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/efficient-animated-content" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/efficient-animated-content" ><span class="devsite-nav-text" tooltip>Use video formats for animated content</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/third-party-summary" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/third-party-summary" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/third-party-summary" ><span class="devsite-nav-text" tooltip>Reduce the impact of third-party code</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/non-composited-animations" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/non-composited-animations" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/non-composited-animations" ><span class="devsite-nav-text" tooltip>Avoid non-composited animations</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/third-party-facades" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/third-party-facades" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/third-party-facades" ><span class="devsite-nav-text" tooltip>Lazy load third-party resources with facades</span></a></li> <li class="devsite-nav-item devsite-nav-heading"><div class="devsite-nav-title devsite-nav-title-no-path"> <span class="devsite-nav-text" tooltip>Diagnostics</span> </div></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/total-byte-weight" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/total-byte-weight" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/total-byte-weight" ><span class="devsite-nav-text" tooltip>Avoid enormous network payloads</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/uses-long-cache-ttl" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/uses-long-cache-ttl" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/uses-long-cache-ttl" ><span class="devsite-nav-text" tooltip>Serve static assets with an efficient cache policy</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/dom-size" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/dom-size" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/dom-size" ><span class="devsite-nav-text" tooltip>Avoid an excessive DOM size</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/critical-request-chains" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/critical-request-chains" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/critical-request-chains" ><span class="devsite-nav-text" tooltip>Avoid chaining critical requests</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/user-timings" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/user-timings" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/user-timings" ><span class="devsite-nav-text" tooltip>User Timing marks and measures</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/bootup-time" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/bootup-time" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/bootup-time" ><span class="devsite-nav-text" tooltip>Reduce JavaScript execution time</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/mainthread-work-breakdown" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/mainthread-work-breakdown" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/mainthread-work-breakdown" ><span class="devsite-nav-text" tooltip>Minimize main thread work</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/font-display" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/font-display" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/font-display" ><span class="devsite-nav-text" tooltip>Ensure text remains visible during webfont load</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/resource-summary" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/resource-summary" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/resource-summary" ><span class="devsite-nav-text" tooltip>Keep request counts low and transfer sizes small</span></a></li> <li class="devsite-nav-item"><a href="/docs/lighthouse/performance/bf-cache" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/bf-cache" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/bf-cache" ><span class="devsite-nav-text" tooltip>Ensure the page can be restored from the back/forward cache</span></a></li> <li class="devsite-nav-item devsite-nav-heading"><div class="devsite-nav-title devsite-nav-title-no-path"> <span class="devsite-nav-text" tooltip>Retired Metrics</span> </div></li> <li class="devsite-nav-item devsite-nav-deprecated"><a href="/docs/lighthouse/performance/interactive" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/interactive" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/interactive" ><span class="devsite-nav-text" tooltip>Time to Interactive</span><span class="devsite-nav-icon material-icons" data-icon="deprecated" data-title="Deprecated" aria-hidden="true"></span></a></li> <li class="devsite-nav-item devsite-nav-deprecated"><a href="/docs/lighthouse/performance/first-meaningful-paint" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/first-meaningful-paint" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/first-meaningful-paint" ><span class="devsite-nav-text" tooltip>First Meaningful Paint</span><span class="devsite-nav-icon material-icons" data-icon="deprecated" data-title="Deprecated" aria-hidden="true"></span></a></li> <li class="devsite-nav-item devsite-nav-deprecated"><a href="/docs/lighthouse/performance/first-cpu-idle" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/first-cpu-idle" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/first-cpu-idle" ><span class="devsite-nav-text" tooltip>First CPU Idle</span><span class="devsite-nav-icon material-icons" data-icon="deprecated" data-title="Deprecated" aria-hidden="true"></span></a></li> <li class="devsite-nav-item devsite-nav-deprecated"><a href="/docs/lighthouse/performance/lighthouse-max-potential-fid" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: /docs/lighthouse/performance/lighthouse-max-potential-fid" track-type="bookNav" track-name="click" track-metadata-eventdetail="/docs/lighthouse/performance/lighthouse-max-potential-fid" ><span class="devsite-nav-text" tooltip>Max Potential First Input Delay</span><span class="devsite-nav-icon material-icons" data-icon="deprecated" data-title="Deprecated" aria-hidden="true"></span></a></li> <li class="devsite-nav-item devsite-nav-heading"><div class="devsite-nav-title devsite-nav-title-no-path"> <span class="devsite-nav-text" tooltip>Resources</span> </div></li> <li class="devsite-nav-item devsite-nav-external"><a href="https://web.dev/learn/performance" class="devsite-nav-title gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Book nav link, pathname: https://web.dev/learn/performance" track-type="bookNav" track-name="click" track-metadata-eventdetail="https://web.dev/learn/performance" ><span class="devsite-nav-text" tooltip>Learn Performance</span><span class="devsite-nav-icon material-icons" data-icon="external" data-title="External" aria-hidden="true"></span></a></li> </ul> <ul class="devsite-nav-list" menu="Docs" aria-label="Side menu" hidden> <li class="devsite-nav-item devsite-nav-heading"> <span class="devsite-nav-title" tooltip > <span class="devsite-nav-text" tooltip > Build with Chrome </span> </span> </li> <li class="devsite-nav-item"> <a href="/docs/web-platform" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Web Platform" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Web Platform </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/capabilities" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Capabilities" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Capabilities </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/chromedriver" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: ChromeDriver" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > ChromeDriver </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/extensions" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Extensions" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Extensions </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/webstore" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Chrome Web Store" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Chrome Web Store </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/chromium" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Chromium" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Chromium </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/aurora" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Aurora" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Aurora </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/android" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Web on Android" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Web on Android </span> </a> </li> <li class="devsite-nav-item"> <a href="https://developer.chrome.com/origintrials/" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Origin trials" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Origin trials </span> </a> </li> <li class="devsite-nav-item"> <a href="/release-notes" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Release notes" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Release notes </span> </a> </li> <li class="devsite-nav-item devsite-nav-heading"> <span class="devsite-nav-title" tooltip > <span class="devsite-nav-text" tooltip > Productivity </span> </span> </li> <li class="devsite-nav-item"> <a href="/docs/devtools" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: DevTools" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > DevTools </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/lighthouse" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Lighthouse" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Lighthouse </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/crux" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Chrome UX Report" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Chrome UX Report </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/accessibility" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Accessibility" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Accessibility </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/workbox" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Workbox" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Workbox </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/puppeteer" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Puppeteer" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Puppeteer </span> </a> </li> <li class="devsite-nav-item devsite-nav-heading"> <span class="devsite-nav-title" tooltip > <span class="devsite-nav-text" tooltip > Experience </span> </span> </li> <li class="devsite-nav-item"> <a href="/docs/ai" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: AI" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > AI </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/performance" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Performance" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Performance </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/css-ui" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: CSS and UI" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > CSS and UI </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/identity" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Identity" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Identity </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/payments" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Payments" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Payments </span> </a> </li> <li class="devsite-nav-item"> <a href="/docs/privacy-security" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Privacy and security" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Privacy and security </span> </a> </li> <li class="devsite-nav-item devsite-nav-heading"> <span class="devsite-nav-title" tooltip > <span class="devsite-nav-text" tooltip > Resources </span> </span> </li> <li class="devsite-nav-item"> <a href="/docs" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: All documentation" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > All documentation </span> </a> </li> <li class="devsite-nav-item"> <a href="https://web.dev/baseline" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: Baseline" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > Baseline </span> </a> </li> <li class="devsite-nav-item"> <a href="https://web.dev" class="devsite-nav-title gc-analytics-event " data-category="Site-Wide Custom Events" data-label="Responsive Tab: web.dev" track-type="navMenu" track-metadata-eventDetail="globalMenu" track-metadata-position="nav"> <span class="devsite-nav-text" tooltip > web.dev </span> </a> </li> </ul> </div> </div> </nav> </devsite-book-nav> <section id="gc-wrapper"> <main role="main" class="devsite-main-content" has-book-nav has-sidebar > <div class="devsite-sidebar"> <div class="devsite-sidebar-content"> <devsite-toc class="devsite-nav" role="navigation" aria-label="On this page" depth="2" scrollbars ></devsite-toc> <devsite-recommendations-sidebar class="nocontent devsite-nav"> </devsite-recommendations-sidebar> </div> </div> <devsite-content> <article class="devsite-article"> <div class="devsite-article-meta nocontent" role="navigation"> <ul class="devsite-breadcrumb-list" aria-label="Breadcrumb"> <li class="devsite-breadcrumb-item "> <a href="https://developer.chrome.com/" class="devsite-breadcrumb-link gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Breadcrumbs" data-value="1" track-type="globalNav" track-name="breadcrumb" track-metadata-position="1" track-metadata-eventdetail="" > Home </a> </li> <li class="devsite-breadcrumb-item "> <div class="devsite-breadcrumb-guillemet material-icons" aria-hidden="true"></div> <a href="https://developer.chrome.com/docs" class="devsite-breadcrumb-link gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Breadcrumbs" data-value="2" track-type="globalNav" track-name="breadcrumb" track-metadata-position="2" track-metadata-eventdetail="Docs" > Docs </a> </li> <li class="devsite-breadcrumb-item "> <div class="devsite-breadcrumb-guillemet material-icons" aria-hidden="true"></div> <a href="https://developer.chrome.com/docs/lighthouse" class="devsite-breadcrumb-link gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Breadcrumbs" data-value="3" track-type="globalNav" track-name="breadcrumb" track-metadata-position="3" track-metadata-eventdetail="Lighthouse" > Lighthouse </a> </li> <li class="devsite-breadcrumb-item "> <div class="devsite-breadcrumb-guillemet material-icons" aria-hidden="true"></div> <a href="https://developer.chrome.com/docs/lighthouse/performance/performance-scoring" class="devsite-breadcrumb-link gc-analytics-event" data-category="Site-Wide Custom Events" data-label="Breadcrumbs" data-value="4" track-type="globalNav" track-name="breadcrumb" track-metadata-position="4" track-metadata-eventdetail="" > Performance audit </a> </li> </ul> <devsite-thumb-rating position="header"> </devsite-thumb-rating> </div> <h1 class="devsite-page-title" tabindex="-1"> Lighthouse performance scoring </h1> <devsite-feature-tooltip ack-key="AckCollectionsBookmarkTooltipDismiss" analytics-category="Site-Wide Custom Events" analytics-action-show="Callout Profile displayed" analytics-action-close="Callout Profile dismissed" analytics-label="Create Collection Callout" class="devsite-page-bookmark-tooltip nocontent" dismiss-button="true" id="devsite-collections-dropdown" dismiss-button-text="Dismiss" close-button-text="Got it"> <devsite-bookmark></devsite-bookmark> <span slot="popout-heading"> Stay organized with collections </span> <span slot="popout-contents"> Save and categorize content based on your preferences. </span> </devsite-feature-tooltip> <div class="devsite-page-title-meta"><devsite-view-release-notes></devsite-view-release-notes></div> <devsite-toc class="devsite-nav" depth="2" devsite-toc-embedded > </devsite-toc> <div class="devsite-article-body clearfix "> <p>How Lighthouse calculates your overall Performance score</p> <p>In general, only <a href="/docs/lighthouse/performance#metrics">metrics</a> contribute to your Lighthouse Performance score, not the results of Opportunities or Diagnostics. That said, improving the opportunities and diagnostics likely improve the metric values, so there is an indirect relationship.</p> <p>Below, we've outlined why the score can fluctuate, how it's comprised, and how Lighthouse scores each individual metric.</p> <h2 id="fluctuations" data-text="Why your score fluctuates" tabindex="-1">Why your score fluctuates</h2> <p>A lot of the variability in your overall Performance score and metric values is not due to Lighthouse. When your Performance score fluctuates it's usually because of changes in underlying conditions. Common problems include:</p> <ul> <li>A/B tests or changes in ads being served</li> <li>Internet traffic routing changes</li> <li>Testing on different devices, such as a high-performance desktop and a low-performance laptop</li> <li>Browser extensions that inject JavaScript and add/modify network requests</li> <li>Antivirus software</li> </ul> <p><a href="https://github.com/GoogleChrome/lighthouse/blob/master/docs/variability.md">Lighthouse's documentation on Variability</a> covers this in more depth.</p> <p>Furthermore, even though Lighthouse can provide you a single overall Performance score, it might be more useful to think of your site performance as a distribution of scores, rather than a single number. See the introduction of <a href="https://web.dev/articles/user-centric-performance-metrics">User-Centric Performance Metrics</a> to understand why.</p> <h2 id="weightings" data-text="How the Performance score is weighted" tabindex="-1">How the Performance score is weighted</h2> <p>The Performance score is a <a href="https://www.wikihow.com/Calculate-Weighted-Average#Weighted_Averages_without_Percentages_sub">weighted average</a> of the <em>metric scores</em>. Naturally, more heavily weighted metrics have a bigger effect on your overall Performance score. The metric scores are not visible in the report, but are calculated under the hood.</p> <aside class="note"><b>Note:</b> The weightings are chosen to provide a balanced representation of the user's perception of performance. The weightings have changed over time because the Lighthouse team is regularly doing research and gathering feedback to understand what has the biggest impact on user-perceived performance.</aside> <figure> <a href="https://googlechrome.github.io/lighthouse/scorecalc/"> <img src="/static/docs/lighthouse/performance/performance-scoring/image/lighthouse-scoring-calcul-196f49058e387.png" alt="Lighthouse scoring calculator webapp" width="600" height="414" srcset="https://developer.chrome.com/static/docs/lighthouse/performance/performance-scoring/image/lighthouse-scoring-calcul-196f49058e387_36.png 36w,https://developer.chrome.com/static/docs/lighthouse/performance/performance-scoring/image/lighthouse-scoring-calcul-196f49058e387_48.png 48w,https://developer.chrome.com/static/docs/lighthouse/performance/performance-scoring/image/lighthouse-scoring-calcul-196f49058e387_72.png 72w,https://developer.chrome.com/static/docs/lighthouse/performance/performance-scoring/image/lighthouse-scoring-calcul-196f49058e387_96.png 96w,https://developer.chrome.com/static/docs/lighthouse/performance/performance-scoring/image/lighthouse-scoring-calcul-196f49058e387_480.png 480w,https://developer.chrome.com/static/docs/lighthouse/performance/performance-scoring/image/lighthouse-scoring-calcul-196f49058e387_720.png 720w,https://developer.chrome.com/static/docs/lighthouse/performance/performance-scoring/image/lighthouse-scoring-calcul-196f49058e387_856.png 856w,https://developer.chrome.com/static/docs/lighthouse/performance/performance-scoring/image/lighthouse-scoring-calcul-196f49058e387_960.png 960w,https://developer.chrome.com/static/docs/lighthouse/performance/performance-scoring/image/lighthouse-scoring-calcul-196f49058e387_1440.png 1440w,https://developer.chrome.com/static/docs/lighthouse/performance/performance-scoring/image/lighthouse-scoring-calcul-196f49058e387_1920.png 1920w,https://developer.chrome.com/static/docs/lighthouse/performance/performance-scoring/image/lighthouse-scoring-calcul-196f49058e387_2880.png 2880w" sizes="(max-width: 840px) 100vw, 856px"> </a> <figcaption class="dcc-caption"> Explore scoring with the <a href="https://googlechrome.github.io/lighthouse/scorecalc/">Lighthouse scoring calculator</a> </figcaption> </figure> <h3 id="lighthouse_10" data-text="Lighthouse 10" tabindex="-1">Lighthouse 10</h3> <div class="table-wrapper"> <table class="with-heading-tint"> <thead> <tr> <th>Audit</th> <th>Weight</th> </tr> </thead> <tbody> <tr> <td><a href="https://web.dev/articles/fcp">First Contentful Paint</a></td> <td>10%</td> </tr> <tr> <td><a href="/en/docs/lighthouse/performance/speed-index">Speed Index</a></td> <td>10%</td> </tr> <tr> <td><a href="https://web.dev/articles/lcp">Largest Contentful Paint</a></td> <td>25%</td> </tr> <tr> <td><a href="https://web.dev/tbt/">Total Blocking Time</a></td> <td>30%</td> </tr> <tr> <td><a href="https://web.dev/articles/cls">Cumulative Layout Shift</a></td> <td>25%</td> </tr> </tbody> </table> </div> <h3 id="lighthouse_8" data-text="Lighthouse 8" tabindex="-1">Lighthouse 8</h3> <div class="table-wrapper"> <table class="with-heading-tint"> <thead> <tr> <th>Audit</th> <th>Weight</th> </tr> </thead> <tbody> <tr> <td><a href="https://web.dev/articles/fcp">First Contentful Paint</a></td> <td>10%</td> </tr> <tr> <td><a href="/en/docs/lighthouse/performance/speed-index">Speed Index</a></td> <td>10%</td> </tr> <tr> <td><a href="https://web.dev/articles/lcp">Largest Contentful Paint</a></td> <td>25%</td> </tr> <tr> <td><a href="https://web.dev/tti/">Time to Interactive</a></td> <td>10%</td> </tr> <tr> <td><a href="https://web.dev/tbt/">Total Blocking Time</a></td> <td>30%</td> </tr> <tr> <td><a href="https://web.dev/articles/cls">Cumulative Layout Shift</a></td> <td>15%</td> </tr> </tbody> </table> </div> <h3 id="metric-scores" data-text="How metric scores are determined" tabindex="-1">How metric scores are determined</h3> <p>Once Lighthouse has gathered the performance metrics (mostly reported in milliseconds), it converts each raw metric value into a metric score from 0 to 100 by looking where the metric value falls on its Lighthouse scoring distribution. The scoring distribution is a log-normal distribution derived from the performance metrics of real website performance data on <a href="https://httparchive.org/">HTTP Archive</a>.</p> <p>For example, Largest Contentful Paint (LCP) measures when a user perceives that the largest content of a page is visible. The metric value for LCP represents the time duration between the user initiating the page load and the page rendering its primary content. Based on real website data, top-performing sites render LCP in about 1,220ms, so that metric value is mapped to a score of 99.</p> <p>Going a bit deeper, the Lighthouse scoring curve model uses HTTPArchive data to determine two control points that then set the shape of a <a href="https://en.wikipedia.org/wiki/Weber%E2%80%93Fechner_law">log-normal</a> curve. The 25th percentile of HTTP Archive data becomes a score of 50 (the median control point), and the 8th percentile becomes a score of 90 (the good/green control point). While exploring the scoring curve plot, note that between 0.50 and 0.92, there's a near-linear relationship between metric value and score. Around a score of 0.96 is the "point of diminishing returns" as higher, the curve pulls away, requiring increasingly more metric improvement to improve an already high score.</p> <figure> <img src="/static/docs/lighthouse/performance/performance-scoring/image/image-the-scoring-curve-f72983bc008e4.png" alt="Image of the scoring curve for TTI" width="600" height="329" srcset="https://developer.chrome.com/static/docs/lighthouse/performance/performance-scoring/image/image-the-scoring-curve-f72983bc008e4_36.png 36w,https://developer.chrome.com/static/docs/lighthouse/performance/performance-scoring/image/image-the-scoring-curve-f72983bc008e4_48.png 48w,https://developer.chrome.com/static/docs/lighthouse/performance/performance-scoring/image/image-the-scoring-curve-f72983bc008e4_72.png 72w,https://developer.chrome.com/static/docs/lighthouse/performance/performance-scoring/image/image-the-scoring-curve-f72983bc008e4_96.png 96w,https://developer.chrome.com/static/docs/lighthouse/performance/performance-scoring/image/image-the-scoring-curve-f72983bc008e4_480.png 480w,https://developer.chrome.com/static/docs/lighthouse/performance/performance-scoring/image/image-the-scoring-curve-f72983bc008e4_720.png 720w,https://developer.chrome.com/static/docs/lighthouse/performance/performance-scoring/image/image-the-scoring-curve-f72983bc008e4_856.png 856w,https://developer.chrome.com/static/docs/lighthouse/performance/performance-scoring/image/image-the-scoring-curve-f72983bc008e4_960.png 960w,https://developer.chrome.com/static/docs/lighthouse/performance/performance-scoring/image/image-the-scoring-curve-f72983bc008e4_1440.png 1440w,https://developer.chrome.com/static/docs/lighthouse/performance/performance-scoring/image/image-the-scoring-curve-f72983bc008e4_1920.png 1920w,https://developer.chrome.com/static/docs/lighthouse/performance/performance-scoring/image/image-the-scoring-curve-f72983bc008e4_2880.png 2880w" sizes="(max-width: 840px) 100vw, 856px"> <figcaption class="dcc-caption"> <a href="https://www.desmos.com/calculator/o98tbeyt1t">Explore the scoring curve for TTI</a>. </figcaption> </figure> <h3 id="desktop" data-text="How desktop versus mobile is handled" tabindex="-1">How desktop versus mobile is handled</h3> <p><a href="#metric-scores">As mentioned</a>, the score curves are determined from real performance data. Prior to Lighthouse v6, all score curves were based on mobile performance data, however a desktop Lighthouse run would use that. In practice, this led to artificially inflated desktop scores. Lighthouse v6 fixed this bug by using specific desktop scoring. While you certainly can expect overall changes in your perf score from 5 to 6, any scores for desktop will be significantly different.</p> <h3 id="color-coding" data-text="How scores are color-coded" tabindex="-1">How scores are color-coded</h3> <p>The metrics scores and the perf score are colored according to these ranges:</p> <ul> <li>0 to 49 (red): Poor</li> <li>50 to 89 (orange): Needs Improvement</li> <li>90 to 100 (green): Good</li> </ul> <p>To provide a good user experience, sites should strive to have a good score (90-100). A "perfect" score of 100 is extremely challenging to achieve and not expected. For example, taking a score from 99 to 100 needs about the same amount of metric improvement that would take a 90 to 94.</p> <h3 id="what_can_developers_do_to_improve_their_performance_score" data-text="What can developers do to improve their performance score?" tabindex="-1">What can developers do to improve their performance score?</h3> <p>First, use the <a href="https://googlechrome.github.io/lighthouse/scorecalc/">Lighthouse scoring calculator</a> to help understand what thresholds you should be aiming for achieving a certain Lighthouse performance score.</p> <p>In the Lighthouse report, the <strong>Opportunities</strong> section has detailed suggestions and documentation on how to implement them. 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